1. Field of the Invention
The present invention pertains to a hydrocarbon fluid well production system wherein electrical power is used to enhance the production of fluids through resistance heating of the fluid bearing formation, and wherein a unique, flexible, coiled tubing is used as an electrical conductor.
2. Background
It has been proposed to produce certain subterranean deposits of viscous hydrocarbonaceous substances by passing an electrical current through the formation to be produced whereby electrical resistance heating renders the viscous hydrocarbons more flowable. U.S. Pat. No. 4,484,627 to Thomas K. Perkins and assigned to the assignee of the present invention, proposes the construction of a well wherein a metallic casing is used as an electrical conductor and as one of the spaced-apart electrodes required in the electrical circuit for enhancing the flow of subterranean hydrocarbon deposits.
Although the system disclosed in the Perkins Patent is directed to overcoming the power losses associated with the use of magnetic casing materials, the well structure is relatively complicated and the non-magnetic metals suitable for casing type conductors are susceptible to rapid rates of corrosion and are relatively expensive to manufacture and install. Moreover, the location of some viscous hydrocarbon deposits, such as in arctic regions, require that essentially no heating of the casing structure be tolerated so as to restrict melting of the permafrost layer of earth and the detrimental effects of same.
Another prior art arrangement of providing downhole electrical power transmission includes running conventional electrical conductors inside the wellbore. The small size of the electrical cable required to be run in the space available in a cased and completed wellbore increases both the system power loss and heat generated in the wellbore itself. Yet another problem associated with such prior art methods includes the relatively slow and cumbersome procedure required when installing conventional electrical conductors in the wellbore, thus increasing the overall well completion costs.
The completion of a cased wellbore using non-metallic casing such as fiberglass or other composite structures has also been proposed. However, presently available non-metallic casing and tubular members are rated at temperatures in the range of approximately 250.degree. F. Production from many wells, considering the wellbore depth and the heat generated by electrical heating may produce fluid temperatures of fluids entering the wellbore in the range of about 400.degree. F.
Accordingly, there have been several problems associated with the development of wells utilizing electrical power transmission to stimulate fluid production that have required or deserve solution in order to improve the viability of this method of enhanced hydrocarbon recovery processes.